1. Field of the Invention
The present invention relates to an improvement in a multicylinder engine intake system comprising: a plurality of throttle bodies having intake paths communicating with intake ports of a multicylinder engine, and throttle valves for opening and closing the intake paths; a plurality of bypasses provided in the throttle bodies, having upstream ends opened to atmosphere or the intake paths on upstream sides of the throttle, and having downstream ends opened to the intake paths on downstream sides of the throttle valves; and a common bypass control valve which opens and closes the bypasses.
2. Description of the Related Art
A multicylinder engine intake system of this type is known from, Japanese Patent Application Laid-open No. 2003-129924. A bypass control valve in this intake system is used to regulate the amount of first idling air supplied to the engine through bypasses in order to appropriately control the first idling rotational speed mainly during engine warm-up operation.
Japanese Patent Application Laid-open No. 2003-129924 discloses an intake system for a V-type 4-cylinder engine in which a common bypass control valve is placed at a central position surrounded by four throttle bodies. In this intake system, the lengths of four bypass downstream paths extending from the bypass control valve to intake paths in the throttle bodies are set equal to each other, thereby equalizing the amounts of first idling air supplied to the cylinders. In this intake system, however, it is necessary to dispose a supporting member for attachment of the bypass control valve separately from the throttle bodies, so that the bypass control valve attachment structure is complicated. Also, in the case of an intake system for an inline 4-cylinder engine, for example, it is difficult to equalize the lengths of four bypass downstream paths by any arrangement of the common bypass control valve.